GCs were first introduced into medicine in the 1950's. Early enthusiasm for these drugs, due to success in controlling inflammation in a wide range of diseases, was soon tempered by the realisation that these compounds cause a very wide range of side effects that were often serious, often irreversible and in many cases more serious than the inflammatory condition under treatment.
The diseases in which GCs have been shown to have a pronounced anti-inflammatory effect include inflammatory arthritides such as rheumatoid arthritis, ankylosing spondylitis and psoriatic arthropathy, other rheumatoid diseases such as systemic lupus erythematosis, scleroderma, vasculitides including temporal arteritis and polyarteritis nodosa, inflammatory bowel disease such as Crohns disease and ulcerative colitis, lung diseases such as asthma and chronic obstructive airways disease, as well as many other conditions such as polymyalgia rheumatica. GCs have also been used very extensively for their immunosuppressive properties in the prevention and treatment of transplant rejection. Finally GCs have been used for their anti-tumour effects in a number of malignancies. The activity of GCs is in the treatment of lymphoproliferative and other malignances is thought to be due to the ability of GCs to induce apoptosis3;4.
The use of GCs, particularly in inflammatory disease, has been severely limited by their side effects that are discussed below. A number of approaches have been taken to overcome the side effects of the drugs. The most frequently adopted approach has been to apply the steroid locally to the site of inflammation. Target organs where this approach has been adopted include the lung with oral inhalation for the treatment of asthma and chronic obstructive airways disease; the nose with local installation for the treatment of allergic rhinitis; the eye with local installation for the treatment of a number of serious inflammatory eye conditions such as uveitis; in large joints with intra-articular injection of steroids to treat inflammation; and on the skin for the treatment of eczema, psoriasis and a range of other conditions of the skin. Local delivery has allowed dose reduction with a consequent reduction in systemic side effects. Systemic side effects have been reduced further by the introduction over recent years of so-called “soft steroids” such as fluticasone for topical application. These soft steroids are inactivated rapidly by metabolism following absorption into the systemic circulation thus minimising systemic side effects. Local application of soft steroids, however, is still associated with significant local side effects such as skin thinning. Soft steroids are of no use when systemic administration of the drug is required in diseases such as temporal arteritis or polymyalgia rheumatica.
The side effects of steroids include the following:
Osteoporosis; growth impairment; avascular osteonecrosis; proximal myopathy; impaired glucose tolerance or frank diabetes; fluid retention and oedema; hypertension; hypokalaemia; Cushingoid faces; weight gain; obesity; euphoria; psychosis; insomnia; raised intracranial pressure; aggravation of epilepsy; memory impairment; hippocampal atrophy; peptic ulceration; pancreatitis; suppression of the hypothalamic pituitary axis; raised introcular pressure; glaucoma; papiloedema; skin thinning; reduced resistance to infection; impaired wound healing.
Despite this catalogue of side effects these drugs are still used very widely because their anti-inflammatory effects exceed those of any other drug class; and they continue to have a central role in the treatment and prevention of transplant rejection and the treatment of lymphoproliferative disorders and certain other malignancies. There is thus a need for novel steroids with the same efficacy as the existing drugs in this class but with a reduced side effect potential.
GCs act via specific glucocorticoid receptors (GR), members of the nuclear receptor superfamily. Hormone binding promotes receptor dimerisation, DNA binding, and transcriptional activation. This mechanism of GC action is well-defined in-vitro, and is critical for regulation of the hypothalamic-pituitary-adrenal axis and gluconeogenesis in-vivo5-8. Hormone bound receptor is also able to influence gene transcription in a dimerisation-independent manner by interfering with the activity of transcription factors, such as AP-1 and NFkB, which are critically involved in the inflammatory reaction.
The induction of apoptosis in thymocytes and other cell types is a well-recognised effect of GCs. The mechanism behind GCs induction of apoptosis is unclear, although it is commonly believed to involve transcriptional activation for example the activation of the caspase pathway9. This remains controversial10-13 and one unexpected finding we made, leading to the first aspect of this invention, was the finding that the activities of GCs in terms of their ability to cause activation, their ability to cause repression and their ability to induce apoptosis could be differentiated. Preferred compounds, as will be discussed below, are those that retain the ability to repress gene expression and induce apoptosis but lose the ability to activate gene expression.
The induction of apoptosis in T lymphocytes may be important to the immunosuppressive activity of GCs. In addition this same mechanism may be important in the anti-inflammatory effects of GCs with the deletion of clonogenic memory T cells responsible for the induction of a response to an antigen14. Finally, there is evidence that in certain diseases, the inflammatory processes may, at least in part, depend on failure of apoptosis in inflammatory cells. This has been shown to be the case with neutrophils in inflammatory bowel diseases15.
After ligand binding, the GR migrates from the cytoplasm of the cell to the nucleus, and binds to glucocorticoid response elements in the regulatory region of target genes. The activated GR then recruits co-factors, including the glucocorticoid receptor interacting protein 1 (GRIP-1) and steroid receptor coactivator 1 (SRC1). These accessory proteins bind to the receptor and link the GR with the general transcription machinery16-22.
Glucocorticoid effects on transcription may be mediated by both the direct binding of activated GR to target DNA, homodimerisation and recruitment of co-activators but also by GR interfering with other transcription factor function, including AP-1, NFkB and NUR7723-31. These two modes of receptor activity are dissociable, that is negative effects on NFkB activity retained but with loss of transactivation. It appears that this second mechanism is largely responsible for mediating the therapeutically desirable anti-inflammatory activity of the GR28;31-33. Interestingly, the IC50 for inhibition of AP-1 or NFkB (0.04 nM) is lower than the EC50 for activation of target genes (5 nM)8;34, yet despite that, high doses of GCs are frequently required to treat patients with inflammatory disease. It appears that cytokines expressed at the site of inflammation may induce relative glucocorticoid resistance, possibly by activating AP-1 or NFkB19;23;31;34-37. This is of importance as the pro-inflammatory cytokines signal by activation of NFkB, and the majority of the anti-inflammatory actions of GCs are thought to be mediated by opposing NFkB action.
Specific mutations in the GR molecule can give rise to dissociated receptors25;25, that is molecules with relatively inactive transactivation compared with transrepression, and a number of synthetic ligands have differential activity on these two GR pathways, for example RU2485838. However, none of the described ligands or molecules has a sufficiently wide dissociation of these two GR actions to be of use therapeutically. In addition RU24858 does not induce apoptosis and hence lacks one of the important activities of GCs, as well as activating the progesterone receptor, thereby having an undesirable lack of specificity of action (unpublished data).
It would be of immense value to identify means to specifically target glucocorticoid action to inhibit NFkB, AP-1 and maintain the ability to induce apoptosis, and at the same time greatly reduce transactivational activity.
Previous studies have tried to differentiate the effects of known and novel steroids in terms of ability to cause transactivation and transrepression39;40. To date no new compounds have been developed. We describe a strategy whereby we were able to identify compounds with useful therapeutic activity.
According to a first aspect of the present invention there is provided a method for treating an inflammatory condition, treating haematological and other malignancies, causing immunosuppression or preventing or treating transplant rejection in man or other animals which comprises administering to a patient a compound that has the structure of Formula I or Formula II as defined below, or a pharmaceutically acceptable derivative thereof or pro-drug therefor

Wherein R═NH2, NHR1, NHOR2, NHNHR2, NHCOR2,
                and R1═C(1-4) alkyl, C(3-6)cycloalkyl,        
                 where n=1-3,        R2=methyl,ethyl,        R3=alkyl, cycloalkyl, substituted alkyl, substituted cycloalkyl, aryl, heteroaryl, substituted aryl, or substituted heteroaryl;        OR        

Wherein R4,R5═C(1-4) alkyl.
The alkyl groups of any of any of R1 to R5 may be straight or branched chain.
In accordance with this method the compounds have been found to induce apoptosis in pro-inflammatory cells.
According to a second aspect of the present invention there is provided a compound according to Formula III or Formula IV defined below:

Wherein R6 and R7 are any of H, CH3CO, CH3CH2CO, CH3CH2CH2CO provided that R6 and R7 are not both H,
OR

Wherein R8 and R9 are any of H, CH3CO, CH3CH2CO or CH3CH2CH2CO.
The compounds having the structure of Formula III or IV are useful as pro-drugs. By the term “pro-drug” is meant a compound that undergoes a chemical conversion to become an active drug when metabolised by the body. This normally results in increased drug effectiveness through an increase of absorption by the body, a prolongation of the duration of action in the body or through a reduction of certain side effects.
According to a third aspect of the present invention there is provided a compound according to Formula I or II as defined above, or a pharmaceutically acceptable derivative thereof or pro-drug therefor, or a compound according to Formula III or IV, for use as a medicine. These compounds are particularly effective in the treatment of an inflammatory condition, for treating haematological and other malignancies, causing immunosuppression or the prevention or treatment of transplant rejection.
According to a fourth aspect of the present invention there is provided the use of a compound according to Formula I or II as defined above, or a pharmaceutically acceptable derivative thereof or pro-drug therefor, or a compound according to Formula III or IV, in the manufacture of a medicament for the treatment of an inflammatory condition, for treating haematological and other malignancies, causing immunosuppression or preventing or treating transplant rejection.
According to a fifth aspect of the present invention there is provided a pharmaceutical composition which comprises a compound according to Formula I or II as defined above, or a pharmaceutically acceptable derivative thereof or pro-drug therefor, or a compound according to Formula III or IV, and a pharmaceutically acceptable carrier. Such a composition has particular use in the treatment of an inflammatory condition, for treating haematological and other malignancies, causing immunosuppression or the prevention or treatment of transplant rejection. The sixth aspect of the present invention is directed to the use of such a composition in the manufacture of a medicament for the treatment of an inflammatory condition, for treating haematological and other malignancies, causing immunosuppression or preventing or treating transplant rejection.
According to a seventh aspect of the present invention there is provided a method of inducing apoptosis in target cells, which comprises administering to the target cells or to the vicinity in which the target cells are located a Compound according to Formula I or II as defined above or a pharmaceutically acceptable derivative thereof or pro-drug therefore, or a compound according to Formula III or IV. The eighth aspect of the present invention is directed to the use of compound according to Formula I or II as defined above or a pharmaceutically acceptable derivative thereof or pro-drug therefor, or a compound according to Formula III or IV, in the manufacture of a medicament for inducing apoptosis in target cells. The target cells are generally pro-inflammatory cells or malignant cells. Thus, this aspect of the invention is useful for treating inflammation and to treat haematological and other malignancies.